The invention relates to the field of the genetic manipulation of plants, particularly the modulation of gene activity and development in plants and increased disease resistance.
Disease in plants is caused by biotic and abiotic causes. Biotic causes include fungi, viruses, bacteria, and nematodes. An example of the importance of plant disease is illustrated by phytopathogenic fungi, which cause significant annual crop yield losses as well as devastating epidemics. Plant disease outbreaks have resulted in catastrophic crop failures that have triggered famines and caused major social change. Pathogenic fungi attack all of the approximately 300,000 species of flowering plants, however, a single plant species can be host to only a few fungal species, and similarly, most fungi usually have a limited host range. Generally, the best strategy for plant disease control is to use resistant cultivars selected or developed by plant breeders for this purpose. However, the potential for serious crop disease epidemics persists today, as evidenced by outbreaks of the Victoria blight of oats and southern corn leaf blight. Molecular methods of crop protection have the potential to implement novel mechanisms for disease resistance and can also be implemented more quickly than traditional breeding methods. Accordingly, molecular methods are needed to supplement traditional breeding methods to protect plants from pathogen attack.
A host of cellular processes enable plants to defend themselves against disease caused by pathogenic agents. These defense mechanisms are activated by initial pathogen infection in a process known as elicitation. In elicitation, the host plant recognizes a pathogen-derived compound known as an elicitor; the plant then activates disease gene expression to limit further spread of the invading microorganism. It is generally believed that to overcome these plant defense mechanisms, plant pathogens must find a way to suppress elicitation as well as to overcome more physically-based barriers to infection, such as reinforcement and/or rearrangement of the actin filament networks near the cell""s plasma membrane.
Thus, the present invention solves needs for enhancement of the plant""s defensive elicitation response via a molecularly based mechanism that can be quickly incorporated into commercial crops.
The present invention provides nucleotide sequences that may find use in modulating development, developmental pathways, and the plant pathogen defense system. Particularly, the nucleotide and amino acid sequences for a sunflower rhoGTPase-Activating Protein (rhoGAP), Lipoxygenase (LOX), Alcohol Dehydrogenase (ADH), and Sclerotinia-Inducible Protein-1 (SCIP-1) are provided.
In particular, the methods and compositions can be used to modulate plant development. More specifically, methods and compositions of the invention may be used for enhancing resistance to plant pathogens including fungal pathogens, plant viruses, and the like. The method involves stably transforming a plant with a nucleotide sequence capable of modulating the plant pathogen defense system operably linked with a promoter capable of driving expression of a gene in a plant cell. The disease resistance genes of the present invention additionally find use in manipulating these processes in transformed plants and plant cells.
Transformed plants, plant cells, and seeds, as well as methods for making such plants, plant cells, and seeds are additionally provided. It is recognized that a variety of promoters will be useful in the invention, the choice of which will depend in part upon the desired level of expression of the disclosed nucleotide sequences. It is recognized that the levels of expression can be controlled to modulate the levels of expression in the plant cell.
Methods and compositions for regulating gene expression in a plant are also provided. Novel nucleotide sequences for inducible plant promoters derived from the LOX and SCIP-1 genes are provided. The methods comprise transforming a plant with a nucleotide sequence of interest operably linked to the LOX or SCIP-1 promoters. Exposure of the transformed plant to a stimulus activates, within the exposed tissue of the plant, transcription of the nucleotide sequence of interest.